The present disclosure is related to downhole tools used in the oil and gas industry and, more particularly, to repeatable position indication for downhole tools.
In the oil and gas industry, knowing where a tool string or work string is located within a wellbore is an essential part of effective hydrocarbon exploration and production. Presently, downhole tool strings employ repeatable collets or snap rings (collectively “position indicators”) that provide positive location indication of the associated downhole tools. In operation, the position indicators are forced into and/or through sized indicator profiles (collectively “indicator profiles”) arranged at predetermined locations within the wellbore. Once the position indicators enter these indicator profiles, an axial “snap” force may be detected or otherwise seen at the surface as the associated spring-loaded components of the position indicators radially expand into the indicator profiles and an axial load change is measured at the surface (i.e., a rig floor).
While conventional position indicators are repeatable, the spring force or snap value of their associated spring-loaded components tends to degrade over time, thereby making it difficult to measure positive location indication at the surface. One solution to this is to manufacture more robust position indicators that exhibit a larger spring force intended to lengthen the useful life of the position indicator. However, if the spring force of a position indicator is too large, various downhole equipment may be damaged, such as seal bores and even the indicator profiles themselves.
Moreover, in some deeper wells, especially in lateral wells where a large portion of the work string lies on the bottom of the wellbore, it is oftentimes difficult to transmit axial loads uphole that can be reliably seen with surface rig equipment. In other applications, the position indicators are required to pass through indicator profiles that are arranged fairly close to each other within the wellbore. In such cases, it is often difficult to determine which indicator profile the position indicator passed through since the tool string can axially bounce upon entering an indicator profile. As a result, ascertaining the difference between axial loads associated with adjacent indicator profiles measured with surface rig equipment can be quite difficult.